Abstract

A 12.5 GHz-spaced optical frequency comb locked to a global positioning system disciplined oscillator for near-infrared (IR) spectrographcalibration is presented. The comb is generated via filtering a 250 MHz-spaced comb. Subsequent nonlinear broadening of the 12.5 GHz comb extends the wavelength range to cover 1380–1820 nm, providing complete coverage over the H-band transmission window of earth’s atmosphere. Finite suppression of spurious sidemodes, optical linewidth, and instability of the comb has been examined to estimate potential wavelength biases in spectrographcalibration. Sidemode suppression varies between 20 and 45 dB, and the optical linewidth is at 1550 nm. The comb frequency uncertainty is bounded by (corresponding to a radial velocity of ), limited by the global positioning system disciplined oscillator reference. These results indicate that this comb can readily support radial velocity measurements below 1 m/s in the near IR.

Received 22 February 2010Accepted 03 May 2010Published online 10 June 2010

Acknowledgments:

We thank T. Fortier for the use of the Ti:sapphire reference comb, Y. Jiang for supplying the subhertz optical reference, Y. Jiang and D. Braje for contributions in building the 250 MHz comb source, M. Lombardi and A. Novick for assistance with the GPSDO, and M. Hirano of Sumitomo Electric Industries for use of the HNLF. Financial support is provided by NSF under Grant No. 0906034 and NIST. F. Quinlan is supported as an NRC/NAS postdoctoral fellow.